U.S. Pat. No. 1,748,185 and 1,894,655 disclose sumps having eduction pipes wit guides which allow relative movement of the eduction pipe relative to the tank bottom within the sump when the car is impacted. The sump extends below the tank bottom an amount sufficient to allow movement of the eduction pipe downwardly without contacting the bottom of the sump.
However for large tank cars the sump must extend below the tank bottom a distance in excess of 1 inch to prevent the eduction pipe from striking the sump bottom when the car is impacted. Such contact can result in damage to the eduction pipe or tank. Current AAR regulations require that if the sump extends below the outside of the tank bottom more than 1 inch a skid is required. The skid adds weight to the car and requires material and labor to install.